Telephone-exchange system.



N0. 559,959. Patentd Oct. I6, |900.

' W. Wl. DAVIS.

TELEPHONE EXCHANGE SYSTEM.

(Application led June 28, IQOQ.)

(N0 Modal.)

nini einen,

IVILLIAM M. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE STROMBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 659,959, dated October 16, 1900. Application tiled June 28, 1900. Serial No. 21,899. (No model.)

To rtZZ whom, t may concern: Be it known that I, WILLIAM M. DAVIS, a citizen of the United States, residing at Chicago, in t-he county of Cook and State oflllinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems, (Case No. 7,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying lo drawing, forming a part of this specification.

My invention relates to multiple-switchboard telephone-exchange systems, and has for its object the provision of improved means for testing the condition of use of called-subscribers telephone-lines.

In accordance with my invention the testthimbles are connected with one terminal of a test-batterythrough the sleeves of the plugs inserted Within the spring-jacks. The other zo terminalof the battery is adapted for connection with the tip of' the testing-plug through the agency of the operators listening-key. The battery that is used for testing may also be used as a common battery for supplying the transmitters at the subscribers stations with current. TWhen the battery thus performs this double function, the tip of the answering-plug is also in electrical connection with the latterterininal of the battery, whereby the test may be rendered inoperative, as the battery-current may follow the tip-strand instead ot' being diverted across the operators telephone set connected in a bridge of the cord-strand. I therefore make that portion of the tip-strand between thev operators telephone set and the answering-plug discontinuous to battery-current, so that in effecting the test the current will have to find path through the operators telephone.

I will explain my invention more fully by reference to the accompanying drawing, illustrating the preferred embodiment thereof, in which a multiple-switchboard telephone-exchange system is diagrammatically illustrated.

The apparatus at substations 10 and 90 is well known to those skilled in the art. A battery-transmitter a, With its coil b, and a receiver c, included in local circuit with a 5s secondary coil (Z, are illustrated at these stations, the primary coil h at each station being adapted for inclusion directly in circuit with the limbs of the corresponding telephoneline through the agency of the telephone switch-hook when the receiver is removed therefrom. A call-bell e, preferably included in circuit with a condenser f, is adapted for inclusion across the limbs of the telephoneline when the receiver at the corresponding station is upon its hook. Other substation apparatus, however, may be employed, if desired. The limbs g and h of each telephoneline extend to line-jacks t' and 7n at sections l and 2 and an answering-jack Z at section 2. A common battery m is connected in bridge between the sides of the telephone-line, having one terminal preferably permanently connected with the limbs g and the other terminal connected With the limbs h through line-indicators n n and the longer or sleeve 7o line-springs of the spring-jacks and their back contacts. The shorter or tip line-springs are connected with the limbs g. The cord-connecting apparatus preferably comprises an answering-plug o and a connecting-plug p, which constitutes the testing-plug, a sleevestrand and a tip-strand uniting the sleeves and tips of the plugs.` Ringing-key springs q q and listening-keysprings r 7' are included in these cord-strands and are normally connected, as illustrated. A key s is provided, which when actuated in one direction serves to include in the circuit operators telephone set t, which is the preferred test-indicator, While When actuated in the other direction it serves to include the calling-generator u in circuit with the called-subscribers signal-bell. A clearing-out indicator fu is included in a bridge connection between the sleeve-strand and the terminal of the battery m, that is immediately connected with the line-indicators, this battery and clearing-out indicator being included in a bridge of the telephonie circuit when the plugs are inserted in the jacks. One terminal of the operators set is connected with that terminal of the battery that has permanent connection With one side of each telephone-line. The other terminal of the operators telephone set is adapted for electrical connection With the tip-strand of the cordcircuit when the handle of the switch-lever s is 'moved to the right. A retardation-coil 'tu is included between the operators telephone set and the spring r of her telephone-key that is included in the tip-strand, the testing-current being passed through the coil lw to the operators telephone set. A condenser-0c may also be employed byl which a resistance y may be shunted. 'Phe test-thimbles of the spring-jacks are electrically connected and are charged with current from the battery m Y through the agency of the sleeve-strand connected with one terminal ot' said battery and the sleeves of the inserted plugs.

A test of a busy line is manifested by a click in the operalors telephone, the testcircuit'being completed from the terminal of the battery that is connected, through the agency of the sleeve-strand and sleeve, with the engaging thimble, to the tip otA the testing-plug, the tip-strand, the retardation-coil w, the operators telephonebeing cut into circuit, the operators telephone, to the other terminal of the battery. The remainder ot' the tip-strand from the corresponding spring fr to the tip of the answering-plug maybe made discontinuous to battery-current by means of condenser e', included in this pertion of the tip-strand, which condenser prevents the battery-current from being shnnted i' away from the operators telephone. If the called-for line is idle, the thimbles will not be charged and no noise will manifest itself in the operators telephone.

Having thus described my invention, I claim as new and desire to secure by Letters Patentl. Ina multipie-switchboard telephone-exchange system, the combination with telephone-lines, each extending from a subscribers station to a plurality of sections of multiple switchboard, sides of the telephone-circuits being connected with tip-contacts of jack-switches, a common battery having one terminal also connected with the said sides,

a cord-circuit having sleeve and tip strands,

the sleeve-strands being connected with t-he remaining terminal of the said common battery, the jacks of the switchboard being provided with electrically-connected .test thim-l bles or contacts adapted for electrical 'connection with the sleeve-strand through the agency of the inserted plugs, an operators telephone set, and aY telephone-key adapted to include the operators telephone set in circuit between the tip-strand and the terminal a cord-circuit having sleeve and tip strands, the sleeve-strands being connected with the remaining terminal of the said common battery, the jacks of the switchboard being provided with electricallyconnected test thimbles or contacts adapted for electrical connection with the sleeve-strand through the agency of the inserted plugs, a testing appliance, and a key adapted to include the testing appliance in circuit. between the tip-strand and the terminal of the battery connected with the tip-contacts of the jacks, the tipstrand being continuous to battery-current between said key and the tip of the connecting-plug, but discontinuous to said current between the key and the answering-plug, substantially as described.

' 3. Ina multiple-switchboard'telephone-exchange system, the combination with telephone-lines each extending from a subscribers station to a plurality ot sections of multiple switchboard, sides of the telephone-circuits being connected with tip-contacts of jack-switches, a common battery havingr one terminal al-so connected with the said sides, a cord-circuit, electrically-connected test-thimbles for the jacks, the plugs of the cord-circuit serving to connect the test-thimbles with the remaining terminal ol said battery, an operators telephone set and a telephone-hey adapted to include the operator-s telephone set in circuit between the tip-strand and the terminal of the battery connected with tipcontacts of the jacks, the tip-strand being continuous to battery-current between said telephone-key and the Iip of the connectingplug, but discontinuous to said current between the telephone-key and the answeringplug, substantially as described.

4. In a multiple-switchboard telephone-exchange system, the combination with lelephone-lines each extending from a subscribers station to a plurality of sections of multiple switchboard, sides of the telephone-circuits being connected with tip-contacts of jack-switches, a common battery having one terminal also connected with the said sides, a cord-circuit, electrically-connected test-thimbles for the jacks, the plugs of the cord-circuit serving to connect the test-thimbles with the remaining terminal of said battery, a testing appliance, and a key adapted to include the testing appliance in circuit between the tip-strand and the terminal ot' the battery connected with tip-contacts of the jacks, the ,tip-strand being continuous to battery-current between said key and the tip of the connecting-plug, but discontinuous to said current between the key and the answerin g-plu g, substantially as described.

In witness whereof I hereuntosubscribe my name-this 18th day of June, A. D. 1900.

WILLIAM M. DAVIS.

Witnesses:

GEORGE L. CRAGG, HARVEY L. HANsoN..

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